(CNN) — Search and rescue operations will intensify Monday morning for victims of a devastating series of tornadoes that ripped through Alabama on Sunday, killing at least 23 people in one county.

The victims including children, died in Lee County, said Sheriff Jay Jones. At least 12 of those deaths occurred in an area about 5 to 6 miles south of the city of Opelika, he said.

Jones told CNN affiliate WRBL that he could not confirm the number of people injured but said that some people were receiving treatment for “very serious injuries.”

Jones described massive damage that appeared “as if someone had taken a blade and just scraped the ground.” He estimated a path of destruction about half a mile wide that stretched several miles to the east from where the tornado touched down.

Searching in quadrants

Late Sunday, Jones told WRBL that Monday’s search would include different agencies, with personnel from all over the state and partner agencies in Georgia.

“We’re going to organize search areas in quadrants and we’re going to start a more intensive search in the morning and cover areas that we’ve already covered and some additional areas as well, primarily in the area where the damage is most significant,” he said. “We’ve done everything we feel like we can do this evening. The area’s just very, very hazardous to put anybody into at this point in time.”

Jones said there had been mass damage to structures, residences and the area and that unmanned aircraft had been using heat-seeking equipment to search some isolated areas.

“Houses completely destroyed, homes — just basically slabs left where once stood a home. Massive damage. In specific areas the contents of one residence we know for a fact were located over 1,000 yards away, so we’ve got a very wide storm track that went through the area — may have even been two storms, we’re not sure. But massive damage.”

Footage broadcast by CNN affiliate WRBL showed trees destroyed by the powerful winds and debris from leveled homes piled up on the side of the road.

Sheriff Jones said a lot of people had volunteered to help but encouraged people to stay at home while authorities tried to secure the damaged area. “Let the first responders, let our search teams, let our EMS personnel — let everyone do their job. That would be of tremendous assistance,” he said.

Jones said a shelter had been established at Providence Baptist Church in the Beauregard community and people trying to locate their loved ones should contact the personnel there.

Five minutes’ warning

CNN Meteorologist Gene Norman said according to National Weather Service data the first tornado warning for Lee County had been issued at 2:58 p.m. ET with the first reports of damage just five minutes later.

It appeared that two tornadoes hit Lee County back-to-back within the span of an hour, Norman said.

A warning for a second tornado was issued at 3:38 p.m. ET with the first reports of damage 13 minutes later.

At least a dozen tornadoes touched down in Alabama and Georgia on Sunday afternoon, according to the NWS.

How the destruction unfolded

  • Tornado watch for Lee County issued 12 p.m. ET
  • Tornado warning 2:58 p.m. ET
  • First reports of damage 3:03 p.m. ET
  • Further damage reports 2:30 p.m. ET
  • Second tornado warning 3:38 p.m ET
  • First reports of damage 3:51 p.m. ET
  • More damage reported 4 p.m. ET

Alabama’s deadliest since 2011

The 23 deaths reported on Sunday marked what would be deadliest day for tornadoes in Alabama since the Tuscaloosa-Birmingham tornado that killed more than 200 people in 2011.

Alabama Gov. Kay Ivey extended the state of emergency that had been issued last month statewide due to tornadoes and severe weather.

“Our hearts go out to those who lost their lives in the storms that hit Lee County today,” she tweeted. “Praying for their families & everyone whose homes or businesses were affected. Officials from @AlabamaEma & other agencies are quickly working to provide assistance.”

It will be a ‘new normal’

Lee County Coroner Bill Harris said coroners from surrounding counties were helping out with the mass casualty event.

“This has been a horrific event for Lee County,” Harris told WRBL. “Just to see all the agencies that have come together and the citizens of this county — to throw out the help they’ve helped for the people that have lost loved ones, that have lost everything that they’ve had is just very heartwarming. “

Rita Smith of the county’s emergency management agency told WRBL that about 150 first responders had been working since the first tornado warning was issued.

“We are heartbroken for the people who have lost loved ones today. It is sad. You prepare and you prepare and you prepare, you guide citizens on what to do and sometimes even when we do everything right, mother nature has a mind of its own. We’re very upset today about this,” Smith said.

She said there had been a lot of devastation.

“When daylight hits tomorrow we’re going to see more, we’re going to see the actual effects of this and it will not be an immediate normal. And when people say ‘you go back to normal’ it’s never normal — it’s a new normal for people who live through things like this. So we’re here to support those people.”

Georgia damage

According to the National Weather Service, an airport in Eufaula, Alabama, along the Alabama-Georgia border was destroyed, along with a fire station.

In Talbotton, Georgia, at least 15 structures were destroyed in a tornado on Sunday, including multiple homes and at least one apartment building, said Leigh Ann Erenheim, the emergency management director for Talbot County.

Six people suffered injuries, with the most severe being a possible broken leg, she said. Crews were checking on residents in the outer areas of town and working to open a shelter for people who have been displaced.

Skip Wyatt, Fire Chief for the Ellerslie Fire Department, told WRBL Sunday night that all the roads in the Georgia community had been shut due to tornado damage.

He said first responders were checking on stranded residents: “I’ve got people trapped in their houses, trapped in their driveways, I’ve pulled guys to go help a guy and his family get untrapped and get them in the house.”

Wyatt warned that residents without power from the downed trees could expect to suffer outages through most of Monday.

The tornadoes are part of the same system that is expected to bring winter weather to much of the eastern United States this week, Norman said.

The NWS warned on Twitter that severe weather would continue into early Monday over the Southeast, with damaging winds, large hail, and isolated tornadoes possible.

CNN’s Brandon Miller, Rashard Rose and Shawn Nottingham contributed to this report.

WHAT OTHERS ARE CLICKING ON:

>>MORE STORIES